The use of sensor technology in the diagnostic medical area is a rapidly expanding field. The use of such sensors can provide a quick and inexpensive method of testing for such things as blood glucose levels by means of resistance measurements.
A prior art sensor is shown in FIGS. 1 and 2. Leads N1 and N2 are formed on the surface of the sensor. An enzyme polymer layer L1 and overcoat L2 (FIG. 2) are formed over the leads. A droplet of blood is applied to the surface of the sensor, causing a reaction with the enzyme layer L1 and the resistance between the leads is measured. This offers a faster, easier and more accurate blood glucose reading than current photo-optic methods. One major problem with silicon based sensors is the cost. Since each sensor will only be used once and then discarded, the cost must be very low.
The major problem which must be overcome in building such a sensor is that the polymer material is very delicate and cannot be subjected to heat or chemicals needed to pattern it. Thus, a method of connecting to terminals N1 and N2 without disturbing the polymer is required. One such prior art method involved etching through the slice and providing backside contacts. This technique, however, leads to high manufacturing costs due to stress and breakage of slices.